Australian Desert Mice: Independence of Exogenous Water

MacMillen, Richard E.; Lee, Anthony K.

doi:10.1126/science.158.3799.383

Cited by 187 publications

(69 citation statements)

References 2 publications

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“…In fact, the maximum ureteral urine to plasma (U/P) ratio in birds is only 2.5, one-tenth of the maximum U/P ratio in mammals (MacMillen and Lee, 1967;Braun and Dantzler, 1972). Therefore, ureteral urine that empties into the urodeum of the cloaca has a relatively high water content.…”

Section: Discussionmentioning

confidence: 99%

Luminal morphology of the avian lower intestine: Evidence supporting the importance of retrograde peristalsis for water conservation

Casotti

2001

Anat. Rec.

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Tissue from the lower intestine of two species of sparrow, the house sparrow Passer domesticus and savannah sparrow Passerculus sandwichensis was sectioned in an unbiased manner and examined quantitatively using stereology. The tissue was processed for light microscopy, and scanning and transmission electron microscopy to examine the extent to which microvilli enhanced the epithelial surface area of the cecae, rectum, and coprodeum. Parameters measured included individual microvillus surface area, microvilli packing density, and absolute surface area. In both species, the average surface area, packing density, and absolute surface area of microvilli decreased distally along the rectum and coprodeum. All three measured variables were not statistically significant (P Ͼ 0.05) between species. Surface area amplification on the cecae due to microvilli was low, and approximated values equivalent to distal regions of the rectum and coprodeum. In the cecae, microvilli within the savannah sparrow had a significantly higher (P Ͻ 0.05) individual surface area, packing density, and absolute surface area than in the house sparrow. The functional implications of a change in microvilli population are discussed in relation to retrograde peristalsis within the lower intestine of birds.

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Section: Discussionmentioning

confidence: 99%

Luminal morphology of the avian lower intestine: Evidence supporting the importance of retrograde peristalsis for water conservation

Casotti

2001

Anat. Rec.

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“…These studies also demonstrate a general trend for species that inhabit arid and semiarid environments to have high abilities to concentrate urine and also high RMT (see also Schmidt-Nielsen 1964;Lee 1967, 1969;Purohit 1974a;Borut and Shkolnik 1974).…”

Section: Introductionmentioning

confidence: 99%

Kidney Mass and Relative Medullary Thickness of Rodents in Relation to Habitat, Body Size, and Phylogeny

Alkahtani

Zuleta²,

Caviedes‐Vidal³

et al. 2004

Physiological and Biochemical Zoology

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We tested the hypotheses that relative medullary thickness (RMT) and kidney mass are positively related to habitat aridity in rodents, after controlling for correlations with body mass. Body mass, mass-corrected kidney mass, mass-corrected RMT, mass-corrected maximum urine concentration, and habitat (scored on a semiquantitative scale of 1-4 to indicate increasing aridity) all showed statistically significant phylogenetic signal. Body mass varied significantly among habitats, with the main difference being that aquatic species are larger than those from other habitats.

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“…PC1 is expressed along the renal tubule, where it is exposed to a wide range of concentrations of urea, from 5 mM in the proximal tubule to up to ϳ1 M in the collecting duct (5)(6)(7). Urea is known as a common denaturant that affects protein function by perturbing their structure (8).…”

Section: Polycystin-1 (Pc1)mentioning

confidence: 99%

Naturally Occurring Osmolytes Modulate the Nanomechanical Properties of Polycystic Kidney Disease Domains

Oberhauser

2010

Journal of Biological Chemistry

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Polycystin-1 (PC1) is a large membrane protein that is expressed along the renal tubule and exposed to a wide range of concentrations of urea. Urea is known as a common denaturing osmolyte that affects protein function by destabilizing their structure. However, it is known that the native conformation of proteins can be stabilized by protecting osmolytes that are found in the mammalian kidney. PC1 has an unusually long ectodomain with a multimodular structure including 16 Ig-like polycystic kidney disease (PKD) domains. Here, we used single-molecule force spectroscopy to study directly the effects of several naturally occurring osmolytes on the mechanical properties of PKD domains. This experimental approach more closely mimics the conditions found in vivo. We show that upon increasing the concentration of urea there is a remarkable decrease in the mechanical stability of human PKD domains. We found that protecting osmolytes such as sorbitol and trimethylamine N-oxide can counteract the denaturing effect of urea. Moreover, we found that the refolding rate of a structurally homologous archaeal PKD domain is significantly slowed down in urea, and this effect was counteracted by sorbitol. Our results demonstrate that naturally occurring osmolytes can have profound effects on the mechanical unfolding and refolding pathways of PKD domains. Based on these findings, we hypothesize that osmolytes such as urea or sorbitol may modulate PC1 mechanical properties and may lead to changes in the activation of the associated polycystin-2 channel or other intracellular events mediated by PC1. Polycystin-1 (PC1)2 is a large transmembrane protein, which, when mutated, cause autosomal dominant polycystic kidney disease (PKD), one of the most common lifethreatening genetic diseases, which is a leading cause of kidney failure (1). The available evidence suggests that PC1 acts as a mechanosensor, receiving signals from the primary (luminal) cilia, neighboring cells, and extracellular matrix and transduces them into cellular responses that regulate proliferation, adhesion, and differentiation that are essential for the control of renal tubules and kidney morphogenesis (1-4).PC1 is expressed along the renal tubule, where it is exposed to a wide range of concentrations of urea, from 5 mM in the proximal tubule to up to ϳ1 M in the collecting duct (5-7). Urea is known as a common denaturant that affects protein function by perturbing their structure (8). Several osmolytes have been found in the mammalian kidney that are known to counteract the effects of urea on proteins (9 -15). Among epithelial cells of the kidney medulla, the principal organic osmolytes include the polyols sorbitol and inositol, the methylamines betaine and glycerophosphocholine, and the amino acid taurine. Protecting osmolytes are found in all taxa (11,14). For example, cartilaginous fish concentrate trimethylamine N-oxide (TMAO), to offset the damaging effects of urea on protein function, and it is one of the best studied protecting osmolytes (e.g. 16 -20).The mecha...

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Australian Desert Mice: Independence of Exogenous Water

Abstract: Certain Australian desert mice can survive and may gain weight on a diet of dry seed without drinking water. Urine concentrations for two of the three species studied are the highest recorded for mammals. The kidneys appear to be the major avenue of water conservation.

Cited by 187 publications

References 2 publications

Luminal morphology of the avian lower intestine: Evidence supporting the importance of retrograde peristalsis for water conservation

Luminal morphology of the avian lower intestine: Evidence supporting the importance of retrograde peristalsis for water conservation

Kidney Mass and Relative Medullary Thickness of Rodents in Relation to Habitat, Body Size, and Phylogeny

Naturally Occurring Osmolytes Modulate the Nanomechanical Properties of Polycystic Kidney Disease Domains

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